The present invention relates to a system in ocean or sea environments for lowering an underwater well head assembly to an underwater well head site while simultaneously extending the associated production pipelines to a central gathering platform. More particularly, this invention relates to such a system for preparing production pipelines and for laying such pipelines between a drilling vessel and a gathering platform in a given time frame which is coextensive with the time frame for drilling of the well. Further, in another time frame, the invention involves coextensively lowering a well head assembly to a well completion position from a drilling vessel with the extension of the associated production pipelines from the well head assembly to the gathering platform.
It is not uncommon in offshore well operations that a central gathering platform is erected at the center or hub of a number of peripherally located wells. The gathering station serves the function of collecting the inputs from the various underwater wells to gather sufficient storage quantities until transfer to a tanker vessel is desired. Alternatively, the storage quantities can be channelled by a large flowline to a land facility or to another oil storage facility in the area.
Heretofore, it has been the practice to complete the peripheral underwater well and, upon completion, install the underwater well head assembly from the drilling vessel. The drilling vessel then is moved off-site to another location while production pipeline laying equipment is moved into position for laying the production pipeline. After laying the pipeline, it is connected underwater to the well head assembly and connected to the gathering platform. These sequential operation functions involve a loss of utility and time for the drilling function of the drilling vessel as well as a time delay in the inputting of production from the well to the gathering station.
The present invention contemplates (1) the preparation and laying of the production pipelines in a time frame coextensive with the drilling of the well and (2) the lowering of a well head assembly with the interconnected pipelines so that a considerable saving in time results which is translatable into decreased costs and production at a much earlier point in time.